In order to save power of mobile devices as well as network resources, a mobile terminal is in an “Idle Mode” when it does not send data, which is also known as “Dormant Mode”. In this mode, there are no links for sessions between the mobile terminal and the network, and thus no wireless resource is used.
In the Idle Mode, the location of the mobile terminal is still necessary to be detected by the network so that the mobile terminal can be waken up into an Active Mode when data needs to be transmitted from the network to the mobile terminal. When the mobile terminal needs to transmit data, it can also return to the Active Mode initiatively. Existing methods for implementing an Idle Mode are illustrated as follows.
1. The mobile terminal monitors a fixed broadcasting channel or paging channel, to acquire network information and parameters of the current location of the mobile terminal. The network information includes a paging group identifier (PG ID) that represents a paging range to which the current location belongs.
2. The mobile terminal updates its location periodically or at a time determined based on detection of network information, so that the network can obtain the latest location information of the mobile terminal.
3. When the network has data to be transmitted, the network may perform a paging procedure in a control channel of the latest location area. The paging message carries the paged terminal information. The mobile terminal in the Idle Mode constantly monitors the message. Once the mobile terminal detects that it is being paged, it enters the Active Mode, and establishes with the network a link used for data transmission and mobile management, and returns to a normal communication state.
Media Independent Handover is also known as MIH. The purpose of providing heterogeneous network handover service is to provide a handover procedure between media of different types, so that a client device can select the best network link automatically when roaming among networks and switch voice channels seamlessly without the user's intervention.
To realize seamless and continuous handover, the MIH is introduced in the existing protocols. Referring to FIG. 1, the MIH is logically defined as a thin layer in the mobility management protocol stack of the terminal device and network and plays a role of an assistant and booster in a handover decision. The upper layer makes a handover decision and link selection based on the input from MIH and the context, and MIH provides the upper layer with some necessary information on handover decision and on how to make the handover decision effectively. An MIH protocol stack mainly includes:
MIH Event Service (MIH-ES), providing event classification, event filtering, and event report of dynamic change events related to link characteristic, link state, and link quality;
MIH Command Service (MIH-CS), providing an MIH user with link operations related to mobility including management, control, and handover; and
MIH Information Service (MIH-IS), providing detailed information of characteristics and services of a serving network and surrounding networks. The information is used for effective system access and handover decision.
The overall architecture model of the MIH is shown in FIG. 2. The MIH provides the upper layer with a universal service interface, the service primitives of the universal interface are independent of the specific protocol stacks of the different access technologies underneath, i.e., the lower layer access technologies are masked. The MIH communicates with the lower layer mobility management protocol stack via a specific interface.
FIG. 3 shows how the system provides the Information Service (IS) in the MIH. The MIIS (MIH IS) serves for handover, and provides a mechanism to discover and acquire the network information within a certain geographic area, including mainly the following functions:
(1) MIIS mainly provides a set of Information Elements (IEs), information structure and representation, inquiry and response mechanism of information transmission;
(2) MIIS may be placed in an MIH function entity, or in an information server;
(3) MIIS information can be acquired via the lower layer or the upper layer; the definition of the information structure may be in XML;
(4) The information can be static, such as a neighbor report; or dynamic, such as link layer parameters (channel information, MAC address, security information, etc.);
(5) MIIS defines a universal representation method for information transmission between different access technologies, such as using a standard format: XML or ASN.1;
(6) MIH-IS provides global information of the network for an MIH user and peer entities. The information is static (i.e. maintainable by the network management), and covers the characteristics and capabilities of the current and surrounding networks, as well as available access networks. The MIH user and the peer entities may use the information for access and handover decision. When maintenance is made by a service provider, the MIH-IS may also be used as a warehouse including handover policy, access priority rule and roaming information, etc. The MIH-IS is a key input in making handover decision.
(7) MIH-IS may receive information from and send information to the MIH layer of a network. The MIH-IS may maintain a profile of the network end in the database. The MIH layer in the terminal devices may acquire from the profile the information of available network for access. The global information can be acquired from the current access point.
MIS-CS command refers to a command issued from the upper layer to the lower layer, including commands from the upper layer to the MIH (such as from the upper layer mobility management protocol stack to the MIH, from the policy engine to the MIH, etc.) and from MIH to the lower layer (MIH to MAC, the MIH to PHY, etc), as well as commands from the local terminal MIH entity to the remote terminal MIH entity. A command mainly carries some instructions that the upper layer makes for the lower layer of the local or peer terminal to control some activities of the lower layer.
MIH events include local events and remote events. The local events are usually sent from the MIH layer to layer 3 mobile protocol layer (L3MP) via a L2 data link (MAC, Radio Link, etc). The remote events are usually sent from the MIH to the peer layer.
Because data links can not be established between different media, the MIH can not support the transmission of remote events between protocol stacks of two media of different types. An event is typically used for handover purposes. The MIH-ES allows the user to receive a notification of the current status and status change of the lower layer transmission link; MIH-ES provides a universal notification interface of link status, and allow the user to make certain personal customization. A typical event is an event for handover detection created for L3MP. For example, an event indicates that in the near future a link will stop transmitting MAC SDUs, L3MP will use this event to prepare to select a new access point before the current link stops transmission, which will reduce the handover time. The events include: Link Up, Link Down, Link Parameters Change, Link Going Down, L2SDU Transmission Status, Link Event Rollback, Pre trigger (L2 Handoff Imminent), etc. The source of an event can be L2 data link (MAC, RRM, etc., different for various access technologies), PHY, or MIH. The destination of the event can be a local or remote MIH, or both. The destination of the event is decided dynamically by a registering mechanism. The receiver of an event can register interested events.
IP Paging may provide management of a user's Dormant Mode, and a mechanism of paging the user in the Dormant Mode. The technology establishes a logical entity in a packet network to manage location information of mobile terminals (or terminal devices) in the Dormant Mode. In the IP Paging technology, location updates and paging messages are transmitted via IP messages. Therefore, an interface of the terminal device shall be able to transmit the IP messages; however, the interface can not transmit the IP messages in the Idle Mode. As the mechanism does not take into consideration the effect of Layer 2 characteristics on media independent paging mechanism, the interface has to be awakened from Dormant Mode to establish an IP connection with the network for transmitting paging messages and location management information. Therefore, load of the mobile terminal is increased and the wireless resource is occupied.